Kafka transport implementation about kit

[sagikazarmark]

I don't think there is a section in the readme for third-party transport implementations, so your may be the first one. I'd say feel free to open a PR and add it somewhere in the readme (maybe below or above the code generator section).

@peterbourgon do you have any preference?

[Reasno]

@alebabai while I appreciate the effort in making this cleanly written and well-documented repo, I think it treats Kafka as a pub/sub, instead of an RPC transport. All other modules in go-kit focus on Request-Response pattern only, including AMQP.

[alebabai]

@Reasno Hi, thanks for feedback.
AMPQ and Nats here are implemented as a pub/sub with RPC concepts (endpoints, request/response), my transport is inspired by them and implemented same way using same principles.

[peterbourgon]

We're not merging new transports, but I'm happy to add a section to the README for this. I think there are probably several more that warrant inclusion. Please open a new PR!